Various forms of wheeled towers for supporting elevated irrigation pipes and moving the irrigation pipes over the ground are provided with trailed wheel track filling structure for filling in the depressed wheel tracks of the wheels of the tower as the tower moves forwardly over the ground. However, most previously known forms of wheel track filling structure can be damaged by rearward movement of the tower and thus a plurality of towers supporting a length of irrigation pipe may not be moved rearwardly until all of the wheel track filling structures thereof have been elevated above the ground. Accordingly, a need exists for structure whereby the wheel track filling structure may be automatically raised above the ground responsive to rearward movement of an associated wheeled irrigation pipe supporting tower.
Examples of various different forms of reversible disk structures as well as other devices including some of the general structural and operational features of the instant invention are disclosed in U.S. Pat. Nos. 2,533,150, 3,640,347, 4,139,018, 4,192,388, 4,209,086 and 4,262,752. However, these previously known devices are not operative in the manner of the instant invention wherein the wheel track filling structure of an irrigation pipe support tower may be automatically raised to an inoperative position responsive to rearward movement of the tower.